The invention relates to a latch, in particular for a motor vehicle with a latch mechanism and with an electrical drive for electrical opening of the latch. A latch mechanism for a door or flap of a motor vehicle demonstrates a locking mechanism which comprises a catch and a pawl for the latching of the catch. The latch comprises a device which ensures first and foremost in an emergency or in the event of breakdown that the latch can be mechanically opened, i.e. without an electrical drive.
The latch initially mentioned serves for the temporary closure of openings in motor vehicles or buildings with the aid of doors or flaps. In the closed state of such a latch, the catch reaches around an in particular bracket-shaped locking bolt which is generally attached to the chassis in the case of a motor vehicle. If the catch reaches a closed position by means of pivoting effected with the aid of the locking bolt starting in an open position, the catch is ultimately locked into place by means of the pawl. A locking area of the pawl is then adjacent to a locking area of the catch, whereby the catch is prevented from being rotated back in the direction of the open position. The locking bolt can no longer leave the locking mechanism in the closed position.
For opening, it is necessary to move the pawl out of its locking position. If the pawl has been moved out of its locking position, the catch rotates in the direction of the open position. In the open position of the catch and thus in the open position of the locking mechanism, the locking bolt can leave the lock. The door or flap can thus be opened again.
There are latches with two different locking positions of the catch. The catch can then initially be latched into the pre-ratcheting position and finally into the so-called main ratcheting position by a further rotation in the closure direction. In the pre-ratcheting position a locking bolt can no longer leave the locking mechanism. However, a relevant door or flap is not yet completely closed. Such a door or flap is only completely closed when the catch is rotated to the main ratcheting position and latched into place here. A second pawl can be provided for latching into place in the pre-ratcheting position.
The latch can comprise a blocking lever which is capable of blocking a pawl if the pawl latches the catch into place. In order to open such a locking mechanism, the blocking lever must first be moved out of its blocking position.
In order to open a latch with particular ease, in the locked state the catch is able to initiate an opening torque into the pawl. The opening torque can cause the pawl to be moved out of its latching position. Such a latch prevents undesirable movement by a blocking lever. If the blocking lever is moved out of its blocking position, the latch then opens automatically. Such a state of the art is known from the publication DE 10 2007 003 948 A1.
There is an activation device to open a latch. The locking mechanism opens when the activation device is activated. A door handle or a flap can be part of the activation device. This handle is generally connected to an activation lever of the latch via a rod or a Bowden cable. If the handle is activated, the activation lever of the latch is pivoted by means of the rod or Bowden cable in such a way that the latch opens. A motor vehicle normally has an external handle which can be accessed from outside, and/or an internal handle which can be accessed from inside.
In accordance with the publication DE 100 48 709 A1 in normal operation the known latch cannot be opened by activation of an external handle, because in normal operation a necessary connection between an activation lever and the locking mechanism is absent. The latch can only be opened from the outside in normal operation with the aid of an electrical drive. However, in an emergency or breakdown the electrical drive makes the mechanical connection between the handle and the locking mechanism in order then to be able to open the latch mechanically in the event of an emergency by activation of the external handle. An emergency is present, for example, in the event of an accident. If a sensor indicates the presence of an emergency, the electrical drive produces the mechanical connection within 10 ms. Such contemporary latches are capable of shifting a latch within 20 ms, such that it can subsequently be opened mechanically.
An airbag sensor can act as a sensor. If an airbag sensor indicates an accident, several milliseconds (ms) of electrical energy are generally available following the signal in order that the mechanical connection can be made by the electrical drive. The electrical energy supply can then fail.
A further sensor can monitor the charging state of a motor vehicle battery. If the charging state of the battery falls below a certain threshold value, this defect can be indicated by the sensor in order to ensure that the electrical drive makes the mechanical connection in order to subsequently enable mechanical opening.